Device and method for biometric verification and registration of a persons identity by means of fingerprint information

ABSTRACT

The invention relates to a device for biometric verification of an individual&#39;s identity by means of fingerprint information, comprising controller and memory means, means for consecutively reading, and storing in said memory means, fingerprint information from partial areas of a finger, and means for extracting, and storing in said memory means, verification data from fingerprint information read from a partial area, moreover comprising means for verification processing of the extracted verification data, the device also comprising decision-making means for deciding if fingerprint information from a new partial area has been read. At least those points in time when fingerprint information from a new partial area has been read are used by the controller means to update the contents of the memory means, said updating comprising removing fingerprint information from previously read partial areas, the controller means also updating the stored verification data on or before said points in time.

TECHNICAL FIELD

[0001] The present invention relates to a device and a method forbiometric verification of an individual's identity by means offingerprint information, and also relates to a device and a method forregistering reference data for use in such biometric verification of anindividual's identity by means of at least one of that individual'sfingerprints. By means of the invention, the memory requirement can bereduced compared to the prior art.

PRIOR ART

[0002] One way of simplifying the use of various types of applianceswhich are protected by, for example, passwords, access codes and thelike, is to replace the codes with devices which recognize the user onthe basis of different physical characteristics, so called biometry. Onetype of biometrical characteristic is fingerprint information, which canbe used to test and either confirm or reject a user's attempt to gainaccess to an appliance, a premises, etc., referred to as user identityverification. Verification with the aid of fingerprint information is inmost cases done by the user having stored his fingerprint information inthe equipment in question in advance, by which means a template iscreated. The information for creating this template can either be inputinto the appliance which the user will later want to have access to, orvia a central appliance.

[0003] When the user attempts to gain access to the equipment inquestion, a biometry device inputs information from the user's fingerand compares the input information to the template in order to decide ifthe user is to be granted access to the equipment or not.

[0004] Equipment which verifies with the aid of fingerprint informationmust satisfy a number of requirements, for example reliability andspeed. For verification to take place in portable devices, for examplemobile telephones, portable computers, different types of cards, etc.,the equipment must additionally be as small, lightweight andenergy-efficient as possible. It is of course also a requirement thatthe equipment should be as inexpensive as possible. These requirementswould also, naturally, improve devices for registering said referenceinformation.

[0005] Known types of devices for verifying a user's identity with theaid of fingerprint information read information from a user'sfingerprint and compare this with a template by means of the inputinformation being combined into a representation of the fingerprint,which is then compared with the template which has been stored inadvance. A disadvantage of such types of equipment is that they requirea great deal of memory, on account of the representation of thefingerprint which is built up. This is also a drawback of know devicesfor registering said reference information. Memory is expensive, takesup space and requires a great deal of current, which means that knowndevices are relatively expensive and large.

[0006] Another parameter which affects cost and takes up space is thesurface area of the sensor which is used to read the fingerprintinformation for the verification. This surface area can be reduced byusing what is referred to as a line sensor, in other words a sensorwhose surface area is too small to read a complete fingerprint withoutthe finger and the sensor moving relative to each other. Duringverification or registering with the aid of such a sensor, the finger ismoved relative to the sensor, and the abovementioned representation ofthe fingerprint is built up in a memory on the basis of consecutivelyinput partial areas. Thus, line sensors satisfy the requirementsregarding the size and cost of the actual sensor, but the requirementfor memory remains. Using a line sensor, the equipment must be able toread information from a moving finger, as distinct from equipment whichuses surface-area sensors, against which the finger is simply placed orheld.

[0007] One example of prior art is SE 515 239, which deals with a methodfor assembling a composite image of a fingerprint, using a sequence ofpartial images. This document appears to deal exclusively withassembling an image of, for example, a fingerprint, and suffers from,inter alia, the abovementioned drawback of a large need for memoryspace.

DISCLOSURE OF THE INVENTION

[0008] There is therefore a need for a device for use in biometricverification of an individual's identity by means of fingerprintinformation, as well as a device for use in registering correspondingreference data for use in said verification. Said device/s shouldrequire much less memory than known types of such devices, and must beable to be used both in the case of stationary reading between a fingerand a sensor of the device, as well as in the case of a relativemovement between the finger and said sensor, the sensor being, forexample, a line sensor.

[0009] This requirement is satisfied by the present invention by makingavailable a device for biometric verification of an individual'sidentity by means of fingerprint information, the device comprisingcontroller means, memory means, means for consecutively reading, andstoring in said memory means, fingerprint information from partial areasof a finger, and means for extracting, and storing in said memory means,verification data from fingerprint information read from a partial area.

[0010] The device also comprises means for verification processing ofthe extracted verification data and decision-making means for decidingif fingerprint information from a new partial area has been read. Atleast those points in time when fingerprint information from a newpartial area has been read are used by the controller means to updatethe contents of the memory means of the device, said updating comprisingremoving fingerprint information from previously read partial areas,with the controller means also updating the stored verification data onor before said points in time.

[0011] Since, according to the invention, at least those points in timewhen fingerprint information from a new partial area has been read areused by the controller means to update the contents of the memory meansof the device, with the controller means also updating the storedverification data on or before said points in time, there is aconsiderable reduction in the memory requirement of the device, and aconsiderable increase in the speed of the processing compared with theprior art.

[0012] Within the scope of the invention, all or select portions of thefingerprint information from previously read partial areas is removedupon said updating, and suitably the decision-making means takes itsdecision only if fingerprint information from an entire new partial areahas been read.

[0013] The updating of stored verification data according to theinvention comprises checking if any of the previously extracted andstored verification data should be exchanged for the verificationinformation extracted most recently, in which case previously extractedverification data may be removed from the memory means of the device.

[0014] In the case of, for example, a line sensor being used for theinvention, the reading means is adapted to manage the reading on thebasis of a relative sliding movement between the finger and the device.

[0015] The need for a device for use in registering correspondingreference data for use in said verification is met by the invention inthat it provides a device for registering reference data for use inverification of an individual's identity by means of at least one ofthat individual's fingerprints, said device comprising controller means,memory means, means for consecutively reading, and storing in saidmemory means, fingerprint information from partial areas of a finger,the device additionally comprising means for extracting, and storing insaid memory means, reference data from fingerprint information read froma partial area, and decision-making means for deciding if fingerprintinformation from a new partial area has been read.

[0016] At least those points in time when fingerprint information from anew partial area has been read are used by the controller means of thedevice to update the contents of the memory means of the device, saidupdating comprising removing fingerprint information from previouslyread partial areas, with the controller means also updating the storedreference data on or before said points in time.

[0017] All, or chosen portions, of fingerprint information frompreviously read partial areas is removed upon said updating, andsuitably the decision-making means takes its decision only iffingerprint information from an entire new partial area has been read.

[0018] Preferably, the updating of stored reference data compriseschecking if any of the previously extracted and stored reference datashould be exchanged for the reference data information extracted mostrecently, in which case previously extracted reference data may beremoved from the memory means of the device.

[0019] In the case of a line sensor being used with the invention, thereading means is adapted to manage the reading on the basis of arelative sliding movement between the finger and the device.

[0020] Since, according to the invention, at least those points in timewhen fingerprint information from a new partial area has been read areused by the controller means to update the contents of the memory meansof the device, with the controller means also updating the storedverification data on or before said points in time, there is aconsiderable reduction in the memory requirement of the device, and aconsiderable increase in the speed of the processing compared with theprior art.

[0021] The invention also relates to methods for use of the devices ofthe invention.

DESCRIPTION OF THE FIGURES

[0022] The invention will be described in more detail below, withreference to the attached drawings, in which:

[0023]FIG. 1 is a schematic view of a finger and of a sensor surface,and

[0024]FIG. 2 shows the treatment of data in the invention.

EMBODIMENTS

[0025] The invention relates to a device and a method for processingfingerprint information, preferably registration and verification ofsaid information in order, for example, to decide if a user is to beallowed to use a certain type of equipment.

[0026] To make the invention easier to understand, a device and a methodfor registration of fingerprint information and extraction of data willfirst be described, after which a verification device and methodaccording to the invention will be described.

[0027]FIG. 1 shows, in a schematic view, a finger F which is placedagainst a sensor which is used to read and register information from thefinger with the aid of a large quantity of sensor elements located in oradjacent to the sensor surface area. The sensor is in this case what isreferred to as a line sensor, in other words a sensor whose total sensorsurface area L is such that the finger and the sensor must be moved inrelation to each other in order to input or read the required quantityof data. This is usually done by the finger being moved at a speed v ina sliding movement across the sensor.

[0028] The sensor covers the area L which is rectangular and contains,by way of example, 32×152 sensor elements, so called pixels. The sensorprinciple according to which the sensor elements work can be chosenlargely arbitrarily, but, by way of example, mention may be made ofoptical sensors, capacitive sensors, heat sensors, and pressure sensors.Each pixel can read a value with a certain resolution, for example 8bits, in other words the value which a pixel reads/inputs can varybetween 0 and 255 bits.

[0029]FIG. 2 is a schematic representation of how information is handledand data is extracted in a device 200 according to the invention. (Theterm “extracted data” here refers to reference data in the case ofregistering, and verification data in the case of verification.)Included in a device 200 according to the invention there is a means Sfor consecutively reading fingerprint information from partial areas ofa finger, which means is expediently a sensor 210, for example thesensor shown in FIG. 1, and a means 230 for extracting certainsignificant data from the information read, and also means 230 forfurther processing these extracted data, as well as a means for controland computing, for example a processor, a CPU, and memory means (notshown in FIG. 2). The extraction and the further processing will bedescribed in detail below. The device moreover comprises adecision-making means 220.

[0030] The functions of these various components in a device accordingto the invention will be explained below on the basis that the sensor Sis a line sensor, but it must be appreciated that the invention canequally well be applied to a device which uses a surface area sensorconsecutively reading partial areas of a stationary finger.

[0031] The reading with the aid of a line sensor 210 involves partialareas of the finger being read by the sensor in connection with themovement of the finger, the partial areas preferably consisting of allor part of the section of the finger which is covering the sensorsurface area, and the extraction and further processing in the means forthis 230 are suitably, but not necessarily, initiated when a completelynew partial area has been read by the sensor 210 or when parts of a newpartial area with an acceptable overlap with the current partial areahave been read.

[0032] The functions of the decision-making means 220 include decidingwhether so much of a new partial area has been read that extraction andfurther processing of data that has been read should be started or notin the means for this 230. When the further processing, and preferablyalso the data extraction, of an partial area which has been read isstarted, the further processing of earlier partial areas is suitablyterminated, and at least these points in time are used by the controllermeans to update the contents of the memory means of the device, saidupdating comprising removing fingerprint information from previouslyread partial areas, with the controller means also updating the storedreference data on or before said points in time.

[0033] According to the invention, all or chosen prtions of fingerprintinformation from previously read partial areas can be removed upon saidupdating. Also, said updating of stored reference data preferablycomprises checking if any of the previously extracted and storedreference data should be exchanged for the reference data informationextracted most recently, in which case previously extracted referencedata may be removed from the memory means of the device.

[0034] This means that large quantities of memory can be saved, sincethe means for further processing 230 never needs to contain more datathan from one partial area, which in principle is also the case for thedecision-making means 220. This too saves memory on account of the factthat data from the partial areas for which the comparison is terminatedcan be removed from the memory.

[0035] The decision-making means 220 can preferably include a memory,for example a RAM, in which data read are stored until so much of a newpartial area has been received that the means 230 for further processingand the means for extraction 230 are to start working on these data. Themeans for further processing and extraction also preferably comprise amemory, for example once again a RAM. The device 200 will also include ameans for control and computing, for example a processor, a CPU. Whenthe decision-making means has decided that data read is to start beingprocessed by the means for extraction and further processing, the datawhich has been read are transferred to the means for extraction andfurther processing, and the decision-making means continues to ascertainwhether a further new partial area has been read.

[0036] The further processing which has been discussed above can eitherinclude the registering of data, which will be used in laterverification of a user's identity, or consist of the actualverification. Both registering and verification with the aid of a deviceaccording to the invention will be explained below.

[0037] In registration with the aid of a device according to theinvention, certain significant data, reference data, are to be extractedso that they can later be used for verification. According to one methodwhich can be used in the present invention, a certain predeterminednumber of what are called significant areas P can be extracted from thetotal area A. One type of significant data which can be used isexplained below, but other types of significant data can also be usedwithin the scope of the invention, for example representation forpattern recognition or so-called minutiae.

[0038] The significant areas P are preferably all of the same size andshape; in the example used here, they are rectangular. In order toextract significant areas P from the sensor area L, a surrounding area Qis used which is smaller than the area L but larger than the significantareas P. The surrounding area Q is preferably also rectangular.

[0039] The sensor area L is regarded as constituting a cartesian systemof coordinates, and the surrounding area Q is initially placed at acertain position in the system of coordinates L, preferably at the upperleft corner of the system of coordinates. In the procedure which iscarried out, the surrounding area Q is thereafter moved in steps withinthe sensor area L, preferably one pixel at a time on the first axis andwith the coordinate on the second axis maintained, thereafter with thecoordinate on the first axis extended by a certain step, preferably onepixel, after which Q with the new coordinate on the first axis is movedone pixel at a time on the second axis, which procedure is repeateduntil the desired part of the sensor area L is covered, or until thedesired number of significant areas P have been found.

[0040] The surrounding area Q can also be regarded as a movable systemof coordinates within the system of coordinates L, with the origin atthe point (x, y) in L. The movement made by Q can then be seen asmovements within L from the origin for Q, in other words movements of xand y.

[0041] For each combination of the values of x and y (in other words foreach position for the origin of Q), a check is made to determine whetherthe partial areas with the predetermined size are unique areas and aretherefore to be stored in a table which can form a basis for laterverification. The condition which determines that an area with thepredetermined size is to be considered as a significant area P is that,within the surrounding area Q, it differs from all other areas ofcorresponding predetermined size according to certain predeterminedconditions which can be varied in a large number of ways. The exactcriteria determining when a partial area is to be considered as uniquein its surroundings can be varied in a number of ways and will thereforenot be described in detail here.

[0042] When the registration process described above has been carriedout for a certain predetermined number of partial areas, the table willcontain the predetermined number of significant areas P. If thepredetermined number of areas have not been found, the registration hasbeen unsuccessful. The table which has been obtained in the registrationprocedure must contain information for each significant area P for lateruse in verification.

[0043] When a user has registered himself in accordance with theprocedure described above, the information which has been stored in thetable can be used at a later stage to verify the user's identity, forexample by means of the above-described type of sensor, in other words aline sensor, that is to say it can be used to decide if the user is tobe allowed access to certain equipment, a building or the like. In thiscase, the means for further processing 230 thus becomes a verificationmeans.

[0044] According to the prior art, for the purpose of furtherprocessing, for example verification, the data read by the line sensorwould be stored and put together to form an image or otherrepresentation of a large part of the fingerprint. However, this wouldrequire a great deal of memory and would entail costs and make theverification equipment relatively large. The present invention offers asolution which permits verification of a user's fingerprint without theneed for large quantities of memory circuits, as will be explainedbelow.

[0045] The actual device and method used for the verification can bevaried within the scope of the invention, but one possible device andmethod is described below. The major components and steps of reading theinformation and extracting data are suitably substantially similar tothose described above in connection with the registration, and will forthat reason not be described again here.

[0046] The verification can be carried out, for example, using a tablewhich has been created in an earlier registration, preferably accordingto the procedure which has been described above, said table includingverification data, i.e. significant data from a number of distinct areasof the user's finger. The table is preferably built up in such a waythat each partial area comes to contain data from one and the samenumber of distinct areas; in the example used below, each partial areacontains two distinct areas.

[0047] The role of the verification means 230 is therefore to ascertainwhether a read partial area contains, with acceptable accuracy, thesignificant areas (i.e. the verification data) from one of the partialareas in the table, which procedure is repeated for a number of thepartial areas which are read. Data from the partial area which is firstread by the sensor 210 are transferred directly to the verificationmeans 230, which examines whether this partial area is identical to oneof several of the partial areas whose data are in the template, forexample the stored partial areas one, two and three. For subsequentpartial areas, the decision-making means 220 will have the same functionas has been described previously in connection with the registration, inother words the decision-making means is used to control when theverification means 230 is to start working with a new partial area.

[0048] When a check is to be made to determine if a read partial area isidentical to one of several of the partial areas whose data are in thetemplate, this is done by examining whether the data available for acertain partial area in the table have an acceptable likeness to acorresponding area in a read partial area. This can be expressed assaying that data in the table become an “operator” applied to the readpartial area to see if it is possible to extract, from the read partialarea, data which has an acceptable likeness to a partial area in thetable.

[0049] If, in the data from a read partial area, it is not possible tofind any correspondences with the data from the significant areas in thetable, the verification is deemed to have been unsuccessful for the readpartial area, and, conversely, if, for a predetermined number ofsignificant areas in the table, it has been possible to findcorrespondences in the read partial areas, the verification is deemed tohave been successful. Regardless of whether the verification of the readpartial area has been successful or not, the read data from this partialarea will be erased when the decision-making means decides that a newpartial area has been read and must be verified.

[0050] When the presence of a certain partial area is considered to havebeen verified, it is possible to use the knowledge of which partial areait was when verifying the partial area which is read thereafter. Forexample, if the partial area which has been read first is verified suchthat it is considered to correspond to partial area number one in thetemplate, it may be sufficient to examine the next partial area to seeif it is partial area number two in the template, and so on. This can bedone in many different ways, and the one which is chosen is not ofcrucial importance to the invention.

[0051] In an alternative of the verification which has been discussedabove, it is possible to extract significant data, for example thesignificant areas according to the above, from the different partialareas and store these data in a table in order, at a later stage, tocompare data in this table with the data which have been saved from theregistration.

[0052] The invention is not limited to the embodiments described aboveand can instead be varied freely within the scope of the attached patentclaims.

[0053] The decision-making means which is included in the invention can,for example, use a large number of different methods for making itsdecision within the scope of the invention. Examples of two such methodswhich may be mentioned here are that the decision-making means caneither measure the speed at which the finger is passed across the sensorand use this to decide when a partial area of a certain size has beenmoved across the sensor, or the decision-making means can usepattern-matching, in other words the decision-making means identifies acertain point in a partial area and examines where this point is locatedin relation to the sensor.

[0054] Moreover, the physical division of the means included in thedevice can of course be made in a large number of ways which are all inprinciple acceptable. As is shown in FIG. 2, the reading means and thedecision-making means can be separate physical units and the extractionmeans can form one unit together with the means for further processing,or each means can be a separate physical unit. All combinations ofphysical and functional units are in principle conceivable within thescope of the invention.

1. Device (200) for biometric verification of an individual's identityby means of fingerprint information, comprising controller means (CPU),memory means, means (S) for consecutively reading, and storing in saidmemory means, fingerprint information from partial areas of a finger,and means (220) for extracting, and storing in said memory means,verification data from fingerprint information read from a partial area,moreover comprising means (230) for verification processing of theextracted verification data, the device also comprising decision-makingmeans (220) for deciding if fingerprint information from a new partialarea has been read, characterized in that at least those points in timewhen fingerprint information from a new partial area has been read areused by the controller means (CPU) to update the contents of the memorymeans of the device, said updating comprising removing fingerprintinformation from previously read partial areas, with the controllermeans also updating the stored verification data on or before saidpoints in time.
 2. Device according to claim 1, in which device allfingerprint information from previously read partial areas is removedupon said updating.
 3. Device according to claim 1 or 2, in which devicesaid decision-making means takes its decision only if fingerprintinformation from an entire new partial area has been read.
 4. Deviceaccording to any of the previous claims, in which said updating ofstored verification data comprises checking if any of the previouslyextracted and stored verification data should be exchanged for theverification information extracted most recently, in which casepreviously extracted verification data may be removed from the memorymeans of the device.